A biosensor is a device that converts information on an analyte into a detectable signal such as a color, fluorescent, or electrical signal using a biological component or imitating the biological component.
Especially, since a biosensor that utilizes a biological enzyme has excellent sensitivity and reaction specificity, it is expected that it will be useful in a wide range of applications such as medical/pharmaceutical field, process measurement in bio-industry, environmental measurement, stability evaluation of chemical materials, etc.
Measurement of chemical components in vitro is medically important, and thus the biosensors are widely used in the analysis of biological samples such as blood in the medical diagnosis field.
Among them, a biosensor using an enzyme analysis method in which a specific reaction between an enzyme and a substrate or between an enzyme and an inhibitor is used has advantages of simple application, excellent detection sensitivity, and fast response, and thus it is most widely used in hospitals and clinical chemistry analysis.
The enzyme analysis method for the measurement of chemical components in vitro may be classified into a chromatogenic method for measuring optical transmittance by a spectroscopic method before and after an enzyme reaction, and an electrode method for measuring an electrochemical signal.
Compared to the electrode method, the chromatogenic method has difficulties in analyzing critical biomaterials because the measurement time is long, a large amount of sample is required, and measurement errors occur due to turbidity in biological samples.
Therefore, the electrode method, in which an electrode system including a plurality of electrodes is formed on a plastic film (insulating substrate) and a reagent is fixed on the electrodes such that a specific substance in a sample can be quantitatively measured by applying a predetermined electric potential to the sample, has been widely applied to the biosensor using the enzyme analysis method.
In the case where the electrode method is employed, a measuring device for obtaining information on biological samples from the biosensor is required, and the measuring device includes a socket electrically connected to thin film electrodes of the biosensor.
Accordingly, when the thin film electrodes of the biosensor are inserted into the measuring device through an inlet port, the thin film electrodes are connected to terminals formed in the socket of the measuring device such that the measuring device in an ON state receives information on the biological material as an analyte from the biosensor.
One of the most widely used biosensors employing the electrode method is a blood glucose meter, with which everyone can measure the concentration of glucose (sugar) in blood by easily taking a drop of blood.
In the case of insulin-dependent diabetics who should measure blood glucose two to three times a day, they take a drop of blood by pricking a finger with a lancet to measure blood glucose. At this time, the blood glucose meter is used to measure blood glucose level from an electrical signal generated by an electrochemical reaction between a reactant in the biosensor and a sample (e.g., blood) taken from a diabetic.
That is, an enzyme reaction layer including a hydrophilic polymer, an oxidoreductase and an electron acceptor is formed on an electrode system of the biosensor such that, when a user injects a sample (blood) containing a substrate (glucose) through a sample inlet port of the biosensor to come in contact with the enzyme reaction layer, the enzyme reaction layer dissolves the sample, the substrate in the sample reacts with an enzyme and is oxidized, and thus the electron acceptor is reduced. At this time, an oxidation current obtained when the reduced electron acceptor is electrochemically oxidized is measured by the measuring device, thereby obtaining the concentration of the substrate contained in the sample.
FIGS. 1 and 2 are diagrams showing a basic configuration of an electrochemical biosensor, in which FIG. 1 is an exploded perspective view and FIG. 2 is an assembly perspective view.
As shown in FIGS. 1 and 2, a biosensor (also referred to as a test strip) 10 includes a working electrode 12 and a reference electrode 13, which are stacked on an upper surface (i.e., inner surface) of a lower insulating substrate 11 in the longitudinal direction, and an enzyme reaction layer, i.e., a reagent reaction layer 14 is fixed on the working electrode 12 and the reference electrode 13 in the width direction. The electrodes 12 and 13 are formed by a thin film formation process such as etching, screen printing, or sputtering.
Moreover, spacers 15 and 16 are stacked on the lower insulating substrate 11 on which the electrodes 12 and 13 are formed such that a sample (e.g., blood) is appropriately introduced into the entire enzyme reaction layer 14. Then, an upper insulating substrate 17 is stacked on the spacers 15 and 16 such that the upper and lower insulating substrates 17 and 11, spaced from each other by the spacers 15 and 16, form a sample path 18 having a capillary structure on the enzyme reaction layer 14.
In this case, the working electrode 12 and the reference electrode 13 are insulated from each other by the spacers 15 and 16, and an inlet of the sample path 18, formed by the upper and lower insulating substrates 17 and 11 through the spacers 15 and 16, corresponds to a sample inlet port 18a through which the sample is injected.
Moreover, each end of the working electrode 12 and the reference electrode 13 is exposed at a connection terminal of the biosensor 10 such that they can be connected to terminals formed in a socket of a measuring device (not shown) when the biosensor 10 is inserted into the measuring device.
Meanwhile, the biosensor (test strip) has an unavoidable error in itself due to various factors. Thus, during manufacturing process of the biosensor, it is determined whether the measurement is accurate or how large the error range is in each biosensor.
Moreover, since it is necessary to correct the error that each biosensor has in order to obtain more accurate measurement, the measuring device receives correction information from the biosensor and corrects the measured value of the biosensor using the correction information, thus displaying a final result value.
For this purpose, a process of inputting the correction information to the measuring device is required due to the error that each biosensor has such that the measuring device can correct the measured value of the biosensor based on the correction information input to the measuring device and display an accurate result value.
For example, the correction information is input to the measuring device in advance such that the measuring device can display a result value obtained by reflecting a correction value (based on the correction information) on the measured value of the corresponding biosensor during measurement. That is, in the case where a blood glucose reference value is 100, if a measured value of a first biosensor is 100, code A is assigned. If a measured value of a second biosensor is 90, code B is assigned to add a correction value of 10, thus making 100. If a measured value of a third biosensor is 110, code C is assigned to subtract 10 from 110, thus making 100. As such, when one of the biosensors is used, a code (indicating the correction information) is input to the measuring device in advance such that the measuring device can display a result value obtained by reflecting the correction value based on the input correction information on the measured value of the corresponding biosensor during the next measurement.
As a conventional method of inputting the correction information to the measuring device, a method of using bar codes is typically used.
That is, after manufacturing biosensors, the manufacturing company obtains correction information by determining error ranges, classifies the biosensors into those having the same correction information (e.g., classified into A, B, and C codes), and contains the biosensors having the same correction information in the same container. Then, the manufacturing company attaches a bar code indicating the corresponding correction formation to the container in which the biosensors having the same correction information are contained and provides the container to a user as a product. Accordingly, the user who has purchased the product reads the bar code attached to the container using a bar code scanner connected to a measuring device and inputs the correction information of the purchased biosensor to the measuring device that the user has.
As a result, the measuring device corrects the measured value of the biosensor based on the correction information input by the bar code scanner during each measurement and displays an accurate result value.
In the above method of using bar codes, a bar code containing a variety of sensor information such as manufacturing date, expiration date, and the type of biosensors contained in the same container as well as the correction information can be printed. Of course, in this case, the biosensors contained in the same container should have the same manufacturing date and expiration date as well as the correction information.
However, the conventional method of using bar codes has the following problems.
In order to input the sensor information including the correction information, it is necessary to read the bar code containing the sensor information, i.e. the bar code attached to the container, and it is thus necessary to connect a scanner to the measuring device, which results in an increase in the price of the measuring device.
Moreover, a biosensor having different sensor information including correction information and the like may be contained in the same container due to carelessness of the manufacturing company or the user. Especially, in the case where the biosensor having different correction information is used by mistake, an accurate correction value of the corresponding biosensor is not reflected (instead, a correction value of the corresponding bar code is reflected), and thereby a measurement error may occur.